An international team led by University of York researchers has directly observed microbial activity in Antarctic and Arctic snow — an environment once considered sterile. The results appear in the Journal of the Royal Society Interface.
Research conducted in laboratories has previously shown that bacteria can stay alive at extremely cold temperatures, but the new study by Redeker et al is the first time that bacteria have been observed altering the polar snow environment in situ. Image credit: Robyn M.
Snow is a highly porous environment, exchanging and entrapping air from the surrounding environment. As more snow is deposited onto the surface of the snowpack, older snow layers compress eventually into ice, encasing small samples of the Earth’s atmosphere existing over and within the snow at the time of deposition.
Climate scientists use ice core samples to look at prehistoric levels of carbon dioxide in the atmosphere so they can be compared with current levels in an industrial age. This analysis of ice cores relies on the assumption that there is limited biological activity altering the environment in the snow during its transition into ice.
The new study has revealed that the composition of these small samples of gas trapped in the ice may have been affected by bacteria that remain active in snow while it is being compressed into ice — a process that can last decades.
“As microbial activity and its influence on its local environment has never been taken into account when looking at ice-core gas samples it could provide a moderate source of error in climate history interpretations,” said lead author Dr. Kelly Redeker, from the Department of Biology at the University of York.
“Respiration by bacteria may have slightly increased levels of carbon dioxide in pockets of air trapped within polar ice caps meaning that before human activity carbon dioxide levels may have been even lower than previously thought.”
“In addition, the fact that we have observed metabolically active bacteria in the most pristine ice and snow is a sign of life proliferating in environments where you wouldn’t expect it to exist. This suggests we may be able to broaden our horizons when it comes to thinking about which planets are capable of sustaining life.”
Dr. Redeker and his colleagues from Northumbria University, the University Centre in Svalbard and the Universities of York and Sheffield looked at snow in is natural state, and in other areas they sterilized it using UV sterilizing lamps.
When they compared the results, the researchers found unexpected levels of iodomethane (methyl iodide) — a gas known to be produced by marine bacteria — in the untouched snow.
Cutting-edge techniques enabled the team to detect the presence of gases even at part-per-trillion levels, one million times less concentrated than atmospheric carbon dioxide concentrations.
The researchers worked on sites in the Arctic and Antarctic and took precautions to limit the impact of sunlight and wind, using tarpaulins to protect their sample sites and positioning themselves on the middle of a glacier away from soil and other forms of polar wildlife which might contaminate the snow.
The results also suggest that life can be sustained even in remote, cold, nutrient poor environments, offering a new perspective on whether the frozen planets of the Universe could support microorganisms.
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K.R. Redeker et al. 2017. Microbial metabolism directly affects trace gases in (sub) polar snowpacks. J. R. Soc. Interface 14 (137); doi: 10.1098/rsif.2017.0729
